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INFERIOR MESENTERIC ARTERY SHEATH PRESERVING-LEFT COLIC ARTERY PRSERVING D3 LYMPHADENECTOMY FOR RECTAL CANCER -FEASIBILITY OF THE TECHNIQUE FROM PATHOLOGICAL POINT OF VIEW-
Leo Yamada^*, Wataru Sakamoto, Daisuke Ujiie, Tomohiro Kikuchi, Mai Ashizawa, Hirokazu Okayama, Katsuharu Saito, Hisahito Endo, Shotaro Fujita, Motonobu Saito, Misato Sakuyama, Hiroshi Nakano, Kenji Gonda, Azuma Nirei, Takeshi Tada, Suguru Hayase, Hiroyuki Hanayama, Kousaku Mimura, Zenichiro Saze, Tomoyuki Momma, Masahiko Shibata, Shinji Ohki, Koji Kono
Gastrointestinal Tract Surgery, Fukushima Medical University, Fukushima, Fukushima, Japan
Background: Sheath of IMA is composed of plexus of autonomic nerve, adipose tissue and collagenous fibers, and it surrounds adventitia of IMA. In the case of anterior resection for rectal cancer, IMA ligation theoretically reduces blood flow to the anastomosis, resulting increase the leakage rate. Therefore,many surgeons employ "Left colic artery (LCA) preserving D3 lymphadenectomy (LCAPD3)"as the standard operational method for rectal cancer.Many reports demonstrate that LCAPD3 showed same overall survival (OS) and relapse free survival (RFS) in the case with rectal cancer as compared to "IMA non-preserving D3 lymphadenectomy".To preserving LCA, at least two techniques are used in Japan;one is IMA sheath preserving LCAPD3 and the other is IMA sheath non-preserving LCAPD3-peeling off the sheath technique. Although IMA sheath preserving LCAPD3 may reduce bleeding from the IMA or post-operative aneurism of IMA,the radicality of lymphadenectomy may be spoiled due to the possibility that lymph node exists in the sheath. To the best of our knowledge, there is no report showing absence of lymph node in the sheath of IMA. The aim of this study is to clarify the feasibility of IMA sheath preserving-LCAPD3 for rectal cancer by pathological investigation.Material and method: In this study, we used rectal and sigmoid cancer specimens with IMA high ligation(n=10).The blood vessel of IMA until LCA branch without peeling off the sheath was used for the investigation, after removing lymph node around IMA for pathological diagnosis for cancer staging.IMA specimens are formalin fixed and paraffin embedded.The sheath IMA and lymph node were observed by H&E stain and the lymphatic duct and lymph node were observed by D2-40 Immunohistochemistry.Then we investigated the existence of lymph node and lymphatic duct in the sheath and measured the thickness of the sheath and diameter of IMA. Results: We found that lymph node did not exist in IMA sheath in all our cases. Average IMA diameter: 2.47mm(±0.37mm), IMA sheath thickness:1.67mm(±0.45mm), distance from IMA to nearest lymphatic duct:70.78mm(±26.99mm), sheath thickness/ IMA diameter: 0.68(±0.14).
Conclusion: There is no lymph node in IMA sheath in our 10 rectal and sigmoid cancer cases. Lymphatic ducts were found in the sheath and they were exist close to the surface of IMA adventitia. These results suggest that it seems to be impossible to remove all of lymphatic duct, even if IMA sheath is peeled off. Based on previous reports that LCAPD3 has the same OS and RPS as compared to IMA high ligation, without preserving the sheath, we conclude that there is no oncological meaning to dissect all the lymphatic duct. In addition, LCAPD3 with IMA sheath preserving is pathologically feasible for rectal cancer. Our study may provide safer operation in terms of intraoperative bleeding from the IMA and post-operative IMA aneurism.

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